1. Field of the Invention
The present invention relates to a solid-state imaging device, a method of manufacturing the solid-state imaging device, and an electronic apparatus.
2. Description of the Related Art
Electronic apparatuses, such as digital video cameras and digital still cameras, include solid-state imaging devices. For example, electronic apparatuses include, as solid-state imaging devices, complementary metal oxide semiconductor (CMOS) image sensors and charge coupled device (CCD) image sensors.
Solid-state imaging devices have a plurality of pixels arranged on the surface of a semiconductor substrate. Each pixel is provided with a photoelectric conversion unit. A photoelectric conversion unit is, for example, a photodiode, and receives light that enters through an externally provided optical system on the light-receiving surface thereof and photoelectrically converts the light, thereby generating signal charge.
In CMOS image sensors among the solid-state imaging devices, pixels are formed in such a manner as to each contain, in addition to a photoelectric conversion unit, a pixel transistor. The pixel transistor is configured to read the signal charge generated by the photoelectric conversion unit, and output it as an electrical signal to a signal line.
Among solid-state imaging devices, there is a “top surface irradiation type” in which light that enters from the top surface side of a semiconductor substrate on which circuit elements, wiring, and the like are provided, is received by a photoelectric conversion unit.
In the case of the “top surface irradiation type”, there is a case in which because circuit elements, wiring and the like shield or reflect light, it is difficult to improve sensitivity.
For this reason, a “bottom surface irradiation type” has been proposed in which a photoelectric conversion unit receives light that enters from the bottom surface side opposite to the top surface of the semiconductor substrate on which circuit elements, wiring, and the like are provided (see, for example, Japanese Patent No. 379435).
In the “bottom surface irradiation type”, it has been proposed that by providing a control electrode for controlling the potential of a photodiode on the top surface side in which wiring and the like are provided, sensitivity and transfer characteristics are improved and also, the occurrence of dark current is suppressed (see, for example, Japanese Unexamined Patent Application Publication No. 2007-258684).